This graph shows the impact of tri-wiring the system with the 1ohm cable and applying the compensation at the speaker terminals. The drop in output is closer to uniform here than for the single wire case or either of the amplifier connection cases. There is small droop in the tweeter section, though. Overall, the change across the 20-20k bandwidth is just a little better.

The droop in the tweeter section is probably due to the LC component placed across the input to the tweeter crossover. It would likely be lessened if a proper zobel had been placed across the tweeter prior to the crossover optimization. I may do this and generate a new crossover to test this aspect. If it helps to make the resultant system more linear when differing cables are used, it will be worthwhile.